SMP300 500W Single Channel Class D Subwoofer Amplifier, Auto Sensing, 4 -8 Ohms, ETL & CE Certified. OSD Audio's SMP300 is a Class D digital mono subwoofer that delivers up to 500W of peak power to reinforce bass in your home theater or audio sound system. Designed for use with passive subwoofers, such as in-wall subwoofers that require external power, the SMP300 provides continuous, stable power, yet stands just 3' tall so it can fit inside any rack or equipment cabinet. Moderately priced with high-end features, this compact sub amp enhances low-frequency sound effects in music and movie soundtracks so you experience precision bass and a richer surround sound experience. The SMP300 includes variable low-pass filter control for consistent, balanced sound quality, as well as variable phase control for additional fine tuning. Multiple connection options include LFE input, line level and speaker level inputs to cover newer and older school source equipment. Characteristics: A compact and powerful digital subwoofer amplifier for home theater applications Efficient Class D digital technology cools under demanding loads Rated at 500W Peak Power and 250W RMS Continuous Includes variable front-panel low-pass filter for balanced, accurate bass Additional front panel controls include phase and volume Multiple input options for older and newer receivers and preamps Auto-sensing function turns off the amplifier when no signal is detected Switchable dual voltage (120V/230V). Variable low pass filter. A front-panel variable low-pass filter lets you adjust the subwoofer's upper frequency limit to control the overlap of the subwoofer's upper frequencies and the main speaker's lower frequencies. This results in bass that complements the sound from the main speakers rather than overpowering them. variable phase control The SMP300 also includes a front panel variable phase control knob that operates in a range of 0 degrees to 180 degrees and allows you to match the arrival times of sound waves from the subwoofer and main speakers. This fine adjustment results in bass that is less muddy or boomy, but smoother and more detailed. Many amp subwoofers in this price range include a variable phase switch that doesn't offer the same amount of audio precision..PZA More Features